Carole Sinfort

Wind-Flow Dynamics Over a Vineyard

Wind-flow dynamics has been extensively studied over horizontally uniform canopies, but agricultural plantations structured in rows such as vineyards have received less attention. Here, the wind flow over a vineyard is studied in neutral stratification from both large-eddy simulation (LES) and in situ measurements. The impact of row structure on the wind dynamics is investigated over a range of wind directions from cross-row to down-row, and a typical range of row aspect ratio (row separation/height ratio). It is shown that the mean flow over a vineyard is similar to that observed in uniform canopies, especially for wind directions from cross-row to diagonal. For down-row winds, the mean flow exhibits noticeable spatial variability across each elementary row-gap pattern, as the wind is channeled in the inter-row. This spatial variability increases with the aspect ratio. With down-row winds the turbulent structures are also more intermittent and generate larger turbulent kinetic energy and momentum flux. The displacement height and roughness length of the vineyard vary with the aspect ratio in a way similar to their variation with canopy density in uniform canopies. Both parameters take smaller values in down-row wind flow, for which the canopy appears more open. The analysis of velocity spectra and autocorrelation functions shows that vineyard canopies share similar features to uniform canopies in terms of turbulent coherent structures, with only minor changes with wind direction.

Development of a rapid methodology for biological efficacy assessment in banana plantations: application to reduced dosages of contact fungicide for Black Leaf Streak Disease (BLSD) control: A methodology to assess biological efficacy of BLSD control

BACKGROUND Black sigatoka is the main disease of banana crop production and is controlled by using either systemic or contact fungicides through spray applications. Biological efficacy is typically assessed on a whole cropping cycle with a natural infestation and periodic spray applications. Developing a faster methodology for assessment of the biological efficacy of a contact fungicide offers promising perspectives for testing current and new fungicides or application techniques. RESULTS The methodology is based on the time of occurrence of the first BLSD symptoms. An artificial infestation protocol was optimized by multiplying the infestation spots and by covering the infested plants. Biological efficacy tests were based on a single spray application after infestation combining three mancozeb dose reductions and two nozzle types. Results demonstrated that a 50% reduction in the mancozeb rated dosage gave significant efficacy independently of the nozzle type, with a reduction of the number of lesions of up to 55% compared with control plants. CONCLUSIONS The described method provides rapid and significant infestation. Further comparison of spray settings and fungicide doses was possible. This methodology will be tested at the plantation scale over a longer period covering the whole crop cycle.

Environmental Impact Evaluation of Cropping Systems Using Life Cycle Assessment: Case Study of Central Tunisia

Semi-arid agricultural areas are fragile territories where water and soil resources must be preserved. In this context, the impact evaluation is difficult due to the lack of data. In this study, we focused on the upstream Merguellil watershed, located in central Tunisia, where several water and soil conservation works (WSCW) were built since 1990 to control water erosion, increase local infiltration and protect the downstream area.